Unless the inching pedal is incorrectly adjusted you should not be having a problem with abrupt starts. The 7 series inching valve is actually pintle-shaped which is meant to improve the feathering of the inching function so it isnt as abrupt, but it is more critical on these transmissions to monitor the transmission clutch apply pressure when adjusting the inching function.

The brake pedal (middle) is used for regular stopping of the truck. The inching pedal on the left is used when you are approaching a rack and want to apply the brakes while gunning the engine to allow the hydraulics to work at full speed, so you can quickly lift the load.

Many drivers use the inching pedal for all braking conditions, and rest their left foot on the pedal which I disagree with. Doing this can hang open the inching valve, decreasing the clutch apply pressure and causing excessive slippage of the clutch packs which will result in increased wear and heat. I think Toyota switching back to two pedals rather than one brake/inching pedal was a good thing, for this very reason.